When unfolded, a conventional folding chair requires several points of fixation in order to remain unchanged in shape. To star folding up the conventional folding chair, a user has to unfasten the points of fixation. Therefore, it is imperative to provide a folding chair not only capable of being unfolded and thus unchangeable in shape but also capable of starting to fold up, because the folding chair has a left engaging portion and a right engaging portion.